U.S. patent application number 13/008429 was filed with the patent office on 2011-08-11 for nozzle mounting structure.
This patent application is currently assigned to MITSUBISHI HEAVY INDUSTRIES, LTD.. Invention is credited to Nobuyuki Hori, Ryuichi Narita, Moritatsu Nishimura, Koji Okimura, Harutaka Suzuki.
Application Number | 20110194663 13/008429 |
Document ID | / |
Family ID | 43838064 |
Filed Date | 2011-08-11 |
United States Patent
Application |
20110194663 |
Kind Code |
A1 |
Hori; Nobuyuki ; et
al. |
August 11, 2011 |
NOZZLE MOUNTING STRUCTURE
Abstract
[Problem] To facilitate mounting of a nozzle. [Solving Means] In
a nozzle mounting structure for mounting a nozzle 20 penetrating
through a reactor vessel 10 having a hemispherical concave inner
surface, the nozzle mounting structure includes a removed concave
portion 17 in which a base material 12 on an inner surface side of
the reactor vessel 10 is removed in a symmetrical shape around a
normal line N on the hemispherical concave inner surface of the
reactor vessel 10, a flange 25 provided on the nozzle 20, formed in
a same symmetrical shape as that of the removed concave portion 17
around the normal line N, and inserted into the removed concave
portion 17, and a weld part 18 provided around the normal line N
for welding the flange 25 to the reactor vessel 10.
Inventors: |
Hori; Nobuyuki; (Tokyo,
JP) ; Narita; Ryuichi; (Tokyo, JP) ;
Nishimura; Moritatsu; (Tokyo, JP) ; Suzuki;
Harutaka; (Tokyo, JP) ; Okimura; Koji; (Tokyo,
JP) |
Assignee: |
MITSUBISHI HEAVY INDUSTRIES,
LTD.
Tokyo
JP
|
Family ID: |
43838064 |
Appl. No.: |
13/008429 |
Filed: |
January 18, 2011 |
Current U.S.
Class: |
376/204 ;
376/352 |
Current CPC
Class: |
G21C 17/017 20130101;
F16L 5/022 20130101; Y02E 30/40 20130101; Y02E 30/30 20130101; G21C
13/036 20130101 |
Class at
Publication: |
376/204 ;
376/352 |
International
Class: |
G21C 13/028 20060101
G21C013/028; G21C 15/00 20060101 G21C015/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 18, 2010 |
JP |
2010-008587 |
Claims
1. A nozzle mounting structure for mounting a nozzle penetrating
through a reactor vessel having a hemispherical concave inner
surface, the nozzle mounting structure comprising: a removed
concave portion in which a base material on an inner surface side
of the reactor vessel is removed in a symmetrical shape around a
normal line on a hemispherical concave inner surface of the reactor
vessel; a flange provided on the nozzle, formed in a same
symmetrical shape as that of the removed concave portion around the
normal line, and inserted into the removed concave portion; and a
weld part provided around the normal line for welding the flange to
the reactor vessel.
2. The nozzle mounting structure of claim 1, wherein the nozzle is
divided into an outer nozzle including the flange and extending to
outside of the reactor vessel, and an inner nozzle arranged inside
of the reactor vessel, which does not include the flange, and the
outer nozzle and the inner nozzle are connected to each other.
3. A nozzle mounting structure for mounting a nozzle penetrating
through a reactor vessel having a hemispherical concave inner
surface, the nozzle mounting structure comprising: a removed
concave portion in which a base material on an inner surface side
of the reactor vessel is removed based on a symmetrical shape
around a centerline of the nozzle; a flange provided on the nozzle,
formed in a symmetrical shape around the centerline, inserted into
the removed concave portion, and protruding to outside of the
removed concave portion; an overlay weld part welded to a surface
of a clad provided on an inner surface of the reactor vessel and
over an outer circumference of the flange protruding to outside of
the removed concave portion around the centerline; and a joint weld
part for welding the flange to the overlay weld part around the
centerline.
4. A nozzle mounting structure for mounting a nozzle penetrating
through a reactor vessel having a hemispherical concave inner
surface, the nozzle mounting structure comprising: a removed
concave portion in which a base material on an inner surface side
of the reactor vessel is removed based on a symmetrical shape
around a centerline of the nozzle; and a weld part provided around
the centerline for welding the nozzle inserted into the removed
concave portion to the reactor vessel.
5. The nozzle mounting structure of claim 4, wherein the nozzle is
divided into an outer nozzle including a welded portion by the
joint weld part and extending to outside of the reactor vessel, and
an inner nozzle arranged inside of the reactor vessel, which does
not include the welded portion by the joint weld part, and the
outer nozzle and the inner nozzle are connected to each other.
6. A nozzle mounting structure for mounting a nozzle penetrating
through a reactor vessel having a hemispherical concave inner
surface, the nozzle mounting structure comprising: a removed
concave portion in which a base material on an inner surface side
of the reactor vessel is removed based on a symmetrical shape
around a centerline of the nozzle; a flange provided on the nozzle,
formed in a symmetrical shape around the centerline, and inserted
into the removed concave portion; a sealing part that seals between
a clad provided on an inner surface of the reactor vessel and the
flange around the centerline; and a fixing part that fixes the
nozzle in a through-hole of the reactor vessel.
7. The nozzle mounting structure of claim 6, wherein the fixing
part is formed by threading between an outer surface of the nozzle
and an inner surface of the through-hole.
8. The nozzle mounting structure of claim 6, wherein the fixing
part is formed by close attachment between an outer surface of the
nozzle being expanded and an inner surface of the through-hole.
9. The nozzle mounting structure according to any one of claims 6
to 8, wherein the sealing part is formed by seal welding.
Description
TECHNICAL FIELD
[0001] The present invention relates to a nozzle mounting structure
for mounting a nozzle on a reactor vessel.
Background Art
[0002] A reactor vessel has a nozzle mounted thereon. The nozzle is
made of stainless steel or Ni-base alloy. Stress corrosion cracking
can be caused in the nozzle by an action of a tensile stress in a
corrosive environment in which high-temperature and high-pressure
water of a reactor cooling material is present. Therefore, it is
possible that the nozzle and a weld part for fixing the nozzle to
the reactor vessel are damaged. Accordingly, repair is performed
according to need and the nozzle is replaced.
[0003] Conventionally, for example, Patent Literature 1 describes a
method of replacing a nozzle fixed and supported by welding with
respect to a weld part on a reactor vessel lower head. According to
this method, after the nozzle fixed and supported in the weld part
on the reactor vessel lower head is respectively cut above and
below the weld part to remove an upper nozzle and a lower nozzle, a
welded part of the reactor vessel is removed together with the
remaining nozzle, and the removed portion is overlay welded and
restored. The lower nozzle is then inserted from a through-hole of
the reactor vessel and fixed to the reactor vessel by welding, and
an insertion end of the lower nozzle is fixed to the upper nozzle
by welding.
CITATION LIST
Patent Literature
[0004] [PTL 1] JP 2530011A
SUMMARY OF INVENTION
Technical Problem
[0005] An inner surface of a reactor vessel lower head has a
hemispherical concave shape, and an existing weld part has a
complicated three-dimensional shape. Therefore, when the weld part
is to be restored, buttered welding is required to the complicated
three-dimensional shape. Further, because the inside of the reactor
vessel is in an underwater environment or an atmospheric
environment with high radiation dose, it is desired to avoid a
manual operation and perform a welding operation by a remote
automatic device. However, buttered welding to a complicated shape
by using the remote automatic device is difficult, and thus
mounting of the nozzle is not easy.
[0006] The present invention has been achieved to solve the above
problems, and an object of the present invention is to provide a
nozzle mounting structure capable of facilitating mounting of a
nozzle.
Solution to Problem
[0007] According to an aspect of the present invention, a nozzle
mounting structure for mounting a nozzle penetrating through a
reactor vessel having a hemispherical concave inner surface,
includes: a removed concave portion in which a base material on an
inner surface side of the reactor vessel is removed in a
symmetrical shape around a normal line on a hemispherical concave
inner surface of the reactor vessel; a flange provided on the
nozzle, formed in a same symmetrical shape as that of the removed
concave portion around the normal line, and inserted into the
removed concave portion; and a weld part provided around the normal
line for welding the flange to the reactor vessel.
[0008] According to the nozzle mounting structure, slotting of the
removed concave portion, positioning of the nozzle in the flange,
and welding of the flange with respect to the reactor vessel can be
performed around the normal line on the hemispherical concave inner
surface of the reactor vessel. Accordingly, mounting of the nozzle
can be easily performed.
[0009] Advantageously, in the nozzle mounting structure, the nozzle
is divided into an outer nozzle including the flange and extending
to outside of the reactor vessel, and an inner nozzle arranged
inside of the reactor vessel, which does not include the flange,
and the outer nozzle and the inner nozzle are connected to each
other.
[0010] According to the nozzle mounting structure, when the weld
part is provided, if the inner nozzle is divided from the outer
nozzle, the inner nozzle is not present in a trajectory for
performing welding in a symmetrical shape around the normal line,
thereby facilitating operations. Further, a forest of nozzles is
present on the inner side of the reactor vessel, and there is only
a narrow space between adjacent nozzles. A wide work space can be
ensured by dividing the inner nozzle from the outer nozzle, thereby
facilitating operations. Accordingly, mounting of the nozzle can be
performed more easily.
[0011] According to another aspect of the present invention, a
nozzle mounting structure for mounting a nozzle penetrating through
a reactor vessel having a hemispherical concave inner surface,
includes: a removed concave portion in which a base material on an
inner surface side of the reactor vessel is removed based on a
symmetrical shape around a centerline of the nozzle; a flange
provided on the nozzle, formed in a symmetrical shape around the
centerline, inserted into the removed concave portion, and
protruding to outside of the removed concave portion; an overlay
weld part welded to a surface of a clad provided on an inner
surface of the reactor vessel and over an outer circumference of
the flange protruding to outside of the removed concave portion
around the centerline; and a joint weld part for welding the flange
to the overlay weld part around the centerline.
[0012] According to the nozzle mounting structure, grooving of the
removed concave portion, positioning of the nozzle in the flange,
and welding of the flange with respect to the reactor vessel can be
performed around the centerline of the nozzle. Accordingly,
mounting of the nozzle can be easily performed. Further, because
the overlay weld part is welded to the surface of the clad and over
the outer circumference of the flange protruding outward of the
removed concave portion, and does not come in contact with the base
material of the removed concave portion, any heating operation is
not required. Therefore, operation processes can be reduced, and
thus mounting of the nozzle can be further facilitated.
[0013] According to still another aspect of the present invention,
a nozzle mounting structure for mounting a nozzle penetrating
through a reactor vessel having a hemispherical concave inner
surface, includes: a removed concave portion in which a base
material on an inner surface side of the reactor vessel is removed
based on a symmetrical shape around a centerline of the nozzle; and
a weld part provided around the centerline for welding the nozzle
inserted into the removed concave portion to the reactor
vessel.
[0014] According to the nozzle mounting structure, grooving of the
removed concave portion, positioning of the nozzle, and welding of
the nozzle with respect to the reactor vessel can be performed
around the centerline of the nozzle. Therefore, mounting of the
nozzle can be easily performed.
[0015] Advantageously, in the nozzle mounting structure, the nozzle
is divided into an outer nozzle including a welded portion by the
joint weld part and extending to outside of the reactor vessel, and
an inner nozzle arranged inside of the reactor vessel, which does
not include the welded portion by the joint weld part, and the
outer nozzle and the inner nozzle are connected to each other.
[0016] According to the nozzle mounting structure, when the joint
weld part is provided, if the inner nozzle is divided from the
outer nozzle, the inner nozzle is not present on the centerline,
thereby facilitating a joint welding operation. Further, a forest
of nozzles is present on the inner side of the reactor vessel, and
there is only a little space between adjacent nozzles. A wide work
space can be ensured by dividing the inner nozzle from the outer
nozzle, thereby facilitating operations. Accordingly, mounting of
the nozzle can be performed more easily.
[0017] According to still another aspect of the present invention,
a nozzle mounting structure for mounting a nozzle penetrating
through a reactor vessel having a hemispherical concave inner
surface, includes: a removed concave portion in which a base
material on an inner surface side of the reactor vessel is removed
based on a symmetrical shape around a centerline of the nozzle; a
flange provided on the nozzle, formed in a symmetrical shape around
the centerline, and inserted into the removed concave portion; a
sealing part that seals between a clad provided on an inner surface
of the reactor vessel and the flange around the centerline; and a
fixing part that fixes the nozzle in a through-hole of the reactor
vessel.
[0018] According to the nozzle mounting structure, grooving of the
removed concave portion, positioning of the nozzle in the flange,
and seal-up and fixation of the flange with respect to the reactor
vessel can be performed around the centerline of the nozzle.
Accordingly, mounting of the nozzle can be easily performed.
Further, because buttered welding is not performed due to having
the sealing part and the fixing part, any buttered welding
operation and heating operation are not required, thereby enabling
to reduce operation processes and to facilitate mounting of the
nozzle.
[0019] Particularly, according to the nozzle mounting structure,
because joint welding, buttered welding, and heat treatment are not
required, construction can be performed in an underwater
environment, and any operation of creating an atmospheric
environment is not required. Accordingly, operation processes can
be considerably reduced, and thus mounting of the nozzle can be
further facilitated.
[0020] Advantageously, in the nozzle mounting structure, the fixing
part is formed by threading between an outer surface of the nozzle
and an inner surface of the through-hole.
[0021] According to the nozzle mounting structure, an operation of
mounting a nozzle can be easily performed.
[0022] Advantageously, in the nozzle mounting structure, the fixing
part is formed by close attachment between an outer surface of the
nozzle being expanded and an inner surface of the through-hole.
[0023] According to the nozzle mounting structure, an operation of
mounting a nozzle can be easily performed.
[0024] Advantageously, in the nozzle mounting structure, the
sealing part is formed by seal welding.
[0025] According to the nozzle mounting structure, a gap between
the clad and the flange can be reliably sealed.
Advantageous Effects of Invention
[0026] According to the present invention, mounting of a nozzle can
be easily performed.
BRIEF DESCRIPTION OF DRAWINGS
[0027] FIG. 1 is a schematic diagram of a nozzle mounting structure
before replacement.
[0028] FIG. 2 is a schematic diagram of a nozzle mounting structure
according to a first embodiment of the present invention.
[0029] FIG. 3 is a schematic diagram of another example of the
nozzle mounting structure according to the first embodiment of the
present invention.
[0030] FIG. 4 is a schematic diagram of another example of the
nozzle mounting structure according to the first embodiment of the
present invention.
[0031] FIG. 5 is a schematic diagram of another example of the
nozzle mounting structure according to the first embodiment of the
present invention.
[0032] FIG. 6 is a schematic diagram of a nozzle mounting structure
according to a second embodiment of the present invention.
[0033] FIG. 7 is a schematic diagram of a nozzle mounting structure
according to a third embodiment of the present invention.
[0034] FIG. 8 is a schematic diagram of a nozzle mounting structure
according to a fourth embodiment of the present invention.
[0035] FIG. 9 is a schematic diagram of another example of the
nozzle mounting structure according to the fourth embodiment of the
present invention.
[0036] FIG. 10 is a schematic diagram of another example of the
nozzle mounting structure according to the fourth embodiment of the
present invention.
[0037] FIG. 11 is a schematic diagram of another example of the
nozzle mounting structure according to the fourth embodiment of the
present invention.
[0038] FIG. 12 is a schematic diagram of a nozzle mounting
structure according to a fifth embodiment of the present
invention.
[0039] FIG. 13 is a schematic diagram of another example of the
nozzle mounting structure according to the fifth embodiment of the
present invention.
DESCRIPTION OF EMBODIMENTS
[0040] Exemplary embodiments of the present invention will be
explained below in detail with reference to the accompanying
drawings. The present invention is not limited to the embodiments.
In addition, constituent elements in the following embodiments
include those that can be replaced by persons skilled in the art or
that are substantially equivalent.
[0041] A nozzle mounting structure explained below is for replacing
a nozzle mounted on a hemispherical lower head in a reactor vessel
in maintenance and repair. As shown in FIG. 1, in the nozzle
mounting structure before replacement, a nozzle 20 is mounted on a
lower head 11 formed in a hemispherical shape, which is a bottom of
a reactor vessel 10, penetrating through the reactor vessel 10.
[0042] A base material 12 of the reactor vessel 10 is made of
carbon steel or low alloy steel. An inner surface of the reactor
vessel 10 is covered with a clad 13 overlay welded with stainless
steel. In the reactor vessel 10, a through-hole 14 for enabling the
nozzle 20 to penetrate therethrough is vertically provided at a
position where the nozzle 20 is mounted. The through-hole 14 has a
weld part 15 at a portion open to the inside of the reactor vessel
10. In the weld part 15, grooving is performed with respect to the
base material 12 inside of the reactor vessel 10, and stainless
steel or Ni-base alloy is overlay welded to a slotted portion (an
overlay weld part 15a). Further, the overlay weld part 15a of the
weld part 15 is slotted, and stainless steel or Ni-base alloy is
joint-welded to the slotted portion (a joint weld part 15b). The
nozzle 20 penetrating through the through-hole 14 is fixed with
respect to the reactor vessel 10 by the joint weld part 15b. The
through-hole 14 has a weld part 16 at a portion open to outside of
the reactor vessel 10. In the weld part 16, stainless steel or
Ni-base alloy is overlay welded.
[0043] The nozzle 20 is formed as an in-core instrumentation tube
for inserting and fixing a detector that measures in-core neutron
flux of the reactor vessel 10. The nozzle 20 is made of stainless
steel or Ni-base alloy. The nozzle 20 is inserted into the
through-hole 14 to penetrate therethrough, and a safe end 21 is
provided at a bottom end thereof extending outside of the reactor
vessel 10. The safe end 21 is fixed to the bottom end of the nozzle
20 by joint welding of stainless steel or Ni-base alloy (a joint
weld part 22). The safe end 21 is connected to a conduit tube 23.
The safe end 21 and the conduit tube 23 are connected to each other
by joint welding of stainless steel (a joint weld part 24).
First Embodiment
[0044] FIG. 2 depicts a nozzle mounting structure according to a
first embodiment of the present invention. As shown in FIG. 2, in
the nozzle mounting structure according to the present embodiment,
the nozzle 20 is detached from the reactor vessel 10 shown in FIG.
1, and a new nozzle 20 is mounted on the reactor vessel 10.
[0045] The nozzle mounting structure includes a removed concave
portion 17 in which the base material 12 at an opening of the
through-hole 14 is removed together with the weld part 15, on an
inner surface side of the reactor vessel 10 after the nozzle 20 has
been detached. The removed concave portion 17 is formed in a
symmetrical shape around a normal line N on a hemispherical concave
inner surface in the lower head 11 of the reactor vessel 10. The
symmetrical shape around the normal line N includes one having a
circular outer diameter around the normal line N and one having a
regular polygonal outer diameter around the normal line N.
[0046] The nozzle mounting structure also includes a flange 25 in
the new nozzle 20. The flange 25 is to be inserted into the removed
concave portion 17, and formed in the same symmetrical shape as
that of the removed concave portion 17 around the normal line
N.
[0047] The nozzle mounting structure also includes a weld part 18
for welding the flange 25 to the reactor vessel 10. The weld part
18 includes an overlay weld part 18a welded to the inner surface of
the removed concave portion 17, and a joint weld part 18b for
welding the flange 25 inserted into the removed concave portion 17
to the overlay weld part 18a. In the overlay weld part 18a,
stainless steel or Ni-base alloy is overlay welded to a slotted
portion of the removed concave portion 17, and in the joint weld
part 18b, stainless steel or Ni-base alloy is joint welded to a
slotted portion of the overlay weld part 18a.
[0048] In a method of forming the nozzle mounting structure, first,
an underwater environment inside the reactor vessel 10 is changed
to an atmospheric environment.
[0049] The removed concave portion 17 is then formed after the
existing nozzle 20 is detached. Specifically, a cutting machine is
arranged around the normal line N on the hemispherical concave
inner surface in the lower head 11 of the reactor vessel 10, to cut
the base material 12 at the opening of the through-hole 14 together
with the weld part 15. Thereafter, a cut groove surface is
externally observed by a camera, and size measurement and PT
testing (penetrant testing) are performed. Accordingly, the removed
concave portion 17 is formed in the symmetrical shape around the
normal line N. Because the removed concave portion 17 is formed
around the normal line N, high accuracy can be ensured.
[0050] Next, the overlay weld part 18a of the weld part 18 is
formed. Specifically, a backing plug is fitted to a portion where
the through-hole 14 is opened in the removed concave portion 17, to
prevent an overlay weld from entering into the through-hole 14.
Thereafter, a heater is fitted along the inner surface of the lower
head 11, which is an outer edge of the removed concave portion 17,
to perform preheating before buttered welding (for example, to
150.degree. C. or higher). A welding apparatus is arranged around
the normal line N to perform buttered welding. Thereafter, the
heater is fitted along the inner surface of the lower head 11,
which is the outer edge of the removed concave portion 17, and the
surface of the overlay weld part 18a, to perform heat treatment
(for example, to 230.degree. C. to 290.degree. C.). Centering and
positioning of a plug cutting and removing device are then
performed with respect to the center of the through-hole 14, the
backing plug is cut and removed, and machining of the through-hole
14 is performed. The heater is then fitted along the inner surface
of the lower head 11, which is the outer edge of the removed
concave portion 17, and the surface of the overlay weld part 18a,
and a heater is arranged inside the through-hole 14 to perform heat
treatment after buttered welding (for example, to 595.degree. C. to
710.degree. C.). It can be considered that the heat treatment after
welding is not required by performing the buttered welding
according to a temper bead welding method. Thereafter, a cutting
device is arranged around the normal line N to form a groove. The
groove surface is externally observed by the camera, and size
measurement and PT testing (penetrant testing) are performed.
Accordingly, the overlay weld part 18a is formed in the symmetrical
shape around the normal line N inside the removed concave portion
17. Because the overlay weld part 18a is formed around the normal
line N, high accuracy can be ensured.
[0051] A new nozzle 20 is inserted into the through-hole 14 from
the inside of the reactor vessel 10, and the flange 25 is fitted to
the overlay weld part 18a. The flange 25 is separately formed in a
factory or the like, and thus high accuracy can be ensured.
[0052] The joint weld part 18b of the weld part 18 is then formed.
Specifically, the welding apparatus is arranged around the normal
line N to perform joint welding. It is then confirmed if there is
any collapse of the nozzle 20 by the camera. Thereafter, a
finishing device is arranged around the normal line N to perform
finishing work. The PT testing (penetrant testing) of the joint
welding is performed. Accordingly, the joint weld part 18b is
formed in the symmetrical shape around the normal line N between
the flange 25 and the overlay weld part 18a. Because the joint weld
part 18b is formed around the normal line N, high accuracy can be
ensured. As a result, the new nozzle 20 is mounted on the reactor
vessel 10.
[0053] In this manner, the nozzle mounting structure according to
the first embodiment described above includes the removed concave
portion 17 in which the base material 12 on the inner surface side
of the reactor vessel 10 is removed in the symmetrical shape around
the normal line N on the hemispherical concave inner surface of the
reactor vessel 10, the flange 25 provided on the nozzle 20, formed
in the same symmetrical shape as that of the removed concave
portion 17 around the normal line N, and inserted into the removed
concave portion 17, and the weld part 18 provided around the normal
line N for welding the flange 25 to the reactor vessel 10.
[0054] According to the nozzle mounting structure, grooving of the
removed concave portion 17, positioning of the nozzle 20 in the
flange 25, and welding of the flange 25 with respect to the reactor
vessel 10 can be performed around the normal line N on the
hemispherical concave inner surface of the reactor vessel 10,
thereby enabling to facilitate mounting of the nozzle 20.
[0055] In the nozzle mounting structure according to the first
embodiment, a mode in which the weld part 18 includes the overlay
weld part 18a and the joint weld part 18b is explained; however,
the present invention is not limited thereto. For example, as
another example of the first embodiment, as shown in FIG. 3, the
weld part 18 can include only the joint weld part 18b.
[0056] In this case, in a method of forming the nozzle mounting
structure, first, an underwater environment inside the reactor
vessel 10 is changed to an atmospheric environment.
[0057] The removed concave portion 17 is formed after the existing
nozzle 20 is detached. Specifically, a cutting machine is arranged
around the normal line N on the hemispherical concave inner surface
in the lower head 11 of the reactor vessel 10, to cut the base
material 12 at the opening of the through-hole 14 together with the
weld part 15. Thereafter, a cut groove surface is externally
observed by a camera, and size measurement and PT testing
(penetrant testing) are performed. Accordingly, the removed concave
portion 17 is formed in the symmetrical shape around the normal
line N. Because the removed concave portion 17 is formed around the
normal line N, high accuracy can be ensured.
[0058] A new nozzle 20 is inserted into the through-hole 14 from
the inside of the reactor vessel 10, and the flange 25 is fitted to
the removed concave portion 17. The nozzle 20 is separately formed
in a factory or the like, and thus high accuracy can be ensured,
including the flange 25.
[0059] The joint weld part 18b of the weld part 18 is then formed.
Specifically, a heater is fitted along the inner surface of the
lower head 11, which is the outer edge of the removed concave
portion 17, to perform preheating before buttered welding (for
example, to 150.degree. C. or higher). A welding apparatus is then
arranged around the normal line N to perform joint welding.
Thereafter, the heater is fitted along the inner surface of the
lower head 11, which is the outer edge of the removed concave
portion 17, and an outer surface of the reactor vessel 10, which is
a circumference of the nozzle 20, to perform heat treatment after
joint welding (for example, to 595.degree. C. to 710.degree. C.).
It is then confirmed if there is any collapse of the nozzle 20 by
the camera. Thereafter, a finishing device is arranged around the
normal line N to perform finishing work. The PT testing (penetrant
testing) of the joint welding is performed. Accordingly, the joint
weld part 18b is formed in the symmetrical shape around the normal
line N between the flange 25 and the removed concave portion 17.
Because the joint weld part 18b is formed around the normal line N,
high accuracy can be ensured. As a result, the new nozzle 20 is
mounted on the reactor vessel 10.
[0060] According to the nozzle mounting structure, because the
overlay weld part 18a (buttered welding) is not required, operation
processes can be reduced, and thus mounting of the nozzle 20 can be
further facilitated.
[0061] As another example of the first embodiment, as shown in
FIGS. 4 and 5, it is desired that the nozzle 20 is divided into an
outer nozzle 20a including the flange 25 and extending to outside
of the reactor vessel 10, and an inner nozzle 20b arranged inside
of the reactor vessel 10, which does not include the flange 25, and
the outer nozzle 20a and the inner nozzle 20b are connected to each
other. Connection between the outer nozzle 20a and the inner nozzle
20b is preferably performed by using a screw joint 26 shown in
FIGS. 4 and 5. Alternatively, connection between the outer nozzle
20a and the inner nozzle 20b can be performed in a form of
generally connecting tubes such as welding or caulking.
[0062] When the joint weld part 18b of the weld part 18 is
provided, if the inner nozzle 20b is divided from the outer nozzle
20b, the inner nozzle 20b is not present in the trajectory for
performing joint welding in a symmetrical shape around the normal
line, thereby facilitating operations. Further, a forest of nozzles
20 is present on the inner side of the reactor vessel 10, and there
is only a narrow space between adjacent nozzles 20. A wide work
space can be ensured by dividing the inner nozzle 20b from the
outer nozzle 20a, thereby facilitating operations. Accordingly,
mounting of the nozzle 20 can be further facilitated. In order that
the inner nozzle 20b is not present in the trajectory for
performing joint welding in the symmetrical shape around the normal
line, it is desired that a divided position between the outer
nozzle 20a and the inner nozzle 20b approaches the flange 25
without limit.
[0063] When the inner nozzle 20b is not divided from the outer
nozzle 20a and the nozzle 20 is integrally constructed as shown in
FIGS. 2 and 3, there is an advantage that any connection work
between the outer nozzle 20a and the inner nozzle 20b is not
required.
Second Embodiment
[0064] A second embodiment of the present invention is explained
with reference to the drawings. As shown in FIG. 6, in the nozzle
mounting structure according to the present embodiment, the nozzle
20 is detached from the reactor vessel 10 shown in FIG. 1, and a
new nozzle 20 is mounted on the reactor vessel 10.
[0065] The nozzle mounting structure includes the removed concave
portion 17 in which the base material 12 at an opening of the
through-hole 14 is removed together with the weld part 15, on an
inner surface side of the reactor vessel 10 after the nozzle 20 has
been detached. The removed concave portion 17 is formed based on a
symmetrical shape around a centerline S of the nozzle 20 (the
through-hole 14 at the time of construction). The symmetrical shape
around the centerline S includes one having a circular outer
diameter around the centerline S and one having a regular polygonal
outer diameter around the centerline S.
[0066] The nozzle mounting structure also includes the flange 25 in
the new nozzle 20. The flange 25 is to be inserted into the removed
concave portion 17 and protrude to outside of the removed concave
portion 17, and formed in the same symmetrical shape as that of the
removed concave portion 17 around the centerline S.
[0067] The nozzle mounting structure also includes the weld part 18
for welding the flange 25 to the reactor vessel 10. The weld part
18 includes the overlay weld part 18a welded to a surface of the
clad 13 provided on the inner surface of the reactor vessel 10
based on the symmetrical shape around the centerline S and over an
outer circumference of the flange 25 protruding to outside of the
removed concave portion 17, and the joint weld part 18b for welding
the flange 25 to the overlay weld part 18a. In the overlay weld
part 18a, stainless steel or Ni-base alloy is overlay welded, and
in the joint weld part 18b, stainless steel or Ni-base alloy is
joint-welded to a slotted portion of the overlay weld part 18a.
[0068] In a method of forming the nozzle mounting structure, first,
an underwater environment inside the reactor vessel 10 is changed
to an atmospheric environment.
[0069] The removed concave portion 17 is formed after the existing
nozzle 20 is detached. Specifically, a cutting machine is arranged
around the centerline S of the through-hole 14, to cut the base
material 12 at the opening of the through-hole 14 together with the
weld part 15. Thereafter, a cut groove surface and the surface of
the clad 13 on which the overlay weld part 18a is formed later are
externally observed by a camera, and size measurement and PT
testing (penetrant testing) are performed. Accordingly, the removed
concave portion 17 is formed based on the symmetrical shape around
the centerline S in a hemispherical concave portion in the lower
head 11 of the reactor vessel 10. Because the removed concave
portion 17 is formed around the centerline S, high accuracy can be
ensured.
[0070] The overlay weld part 18a of the weld part 18 is provided
next. Specifically, a backing plug is fitted to a portion where the
removed concave portion 17 is opened, to prevent an overlay weld
from entering into the removed concave portion 17. Thereafter, a
welding device is arranged around the centerline S to perform
buttered welding on the surface of the clad 13. Centering and
positioning of a plug cutting and removing device are then
performed with respect to the centerline S of the through-hole 14,
the backing plug is cut and removed, and machining of the overlay
weld part 18a and the through-hole 14 is performed. Thereafter, the
cutting device is arranged around the centerline S to form a
groove. A groove surface is externally observed by the camera, and
size measurement and PT testing (penetrant testing) are performed.
Accordingly, the overlay weld part 18a is formed based on the
symmetrical shape around the centerline S on the surface of the
clad 13, which is the outer edge of the removed concave portion 17.
Because the overlay weld part 18a is formed around the centerline
S, high accuracy can be ensured.
[0071] A new nozzle 20 is inserted into the through-hole 14 from
the inside of the reactor vessel 10, and the flange 25 is fitted
into the overlay weld part 18a. The nozzle 20 is separately formed
in a factory or the like, and thus high accuracy can be ensured
while including the flange 25.
[0072] The joint weld part 18b of the weld part 18 is then formed.
Specifically, the welding apparatus is arranged around the
centerline S to perform joint welding. It is then confirmed if
there is any collapse of the nozzle 20 by the camera. Thereafter, a
finishing device is arranged around the centerline S to perform
finishing work. The PT testing (penetrant testing) of the joint
welding is performed. Accordingly, the joint weld part 18b is
formed in the symmetrical shape around the centerline S between the
flange 25 and the overlay weld part 18a. Because the joint weld
part 18b is formed around the centerline S, high accuracy can be
ensured. As a result, the new nozzle 20 is mounted on the reactor
vessel 10.
[0073] In this manner, the nozzle mounting structure according to
the second embodiment described above includes the removed concave
portion 17 in which the base material 12 on the inner surface side
of the reactor vessel 10 is removed based on the symmetrical shape
around the centerline S of the nozzle 20, the flange 25 provided on
the nozzle 20, formed in the symmetrical shape around the
centerline S, and inserted into the removed concave portion 17 and
protruding to outside of the removed concave portion 17, the
overlay weld part 18a welded to the surface of the clad 13 provided
on the inner surface of the reactor vessel 10 based on the
symmetrical shape around the centerline S and over the outer
circumference of the flange 25 protruding to the outside of the
removed concave portion 17, and the joint weld part 18b for welding
the flange 25 to the overlay weld part 18a around the centerline
S.
[0074] According to the nozzle mounting structure, grooving of the
removed concave portion 17, positioning of the nozzle 20 in the
flange 25, and welding of the flange 25 with respect to the reactor
vessel 10 can be performed around the centerline of the nozzle 20,
thereby enabling to facilitate mounting of the nozzle 20. Further,
because the overlay weld part 18a is welded to the surface of the
clad 13 and over the outer circumference of the flange 25
protruding to the outside of the removed concave portion 17, and
does not come in contact with the base material 12 of the removed
concave portion 17, any heating operation is not required.
Therefore, operation processes can be reduced, and thus mounting of
the nozzle 20 can be further facilitated.
Third Embodiment
[0075] A third embodiment of the present invention is explained
with reference to the drawings. As shown in FIG. 7, in the nozzle
mounting structure according to the present embodiment, the nozzle
20 is detached from the reactor vessel 10 shown in FIG. 1, and a
new nozzle 20 is mounted on the reactor vessel 10.
[0076] The nozzle mounting structure includes the removed concave
portion 17 in which the base material 12 at an opening of the
through-hole 14 is removed together with the weld part 15, on an
inner surface side of the reactor vessel 10 after the nozzle 20 has
been detached. The removed concave portion 17 is formed based on a
symmetrical shape around the centerline S of the nozzle 20 (the
through-hole 14 at the time of construction). The symmetrical shape
around the centerline S includes one having a circular outer
diameter around the centerline S and one having a regular polygonal
outer diameter around the centerline S.
[0077] The nozzle mounting structure includes the weld part 18 for
welding a new nozzle 20 to the reactor vessel 10. The weld part 18
includes the overlay weld part 18a welded to an inner surface of
the removed concave portion 17 around the centerline S and the
joint weld part 18b for welding the nozzle 20 to the overlay weld
part 18a around the centerline S. In the overlay weld part 18a,
stainless steel or Ni-base alloy is overlay welded, and in the
joint weld part 18b, stainless steel or Ni-base alloy is
joint-welded to a slotted portion of the overlay weld part 18a.
[0078] In a method of forming the nozzle mounting structure, first,
an underwater environment inside the reactor vessel 10 is changed
to an atmospheric environment.
[0079] The removed concave portion 17 is then formed after the
existing nozzle 20 is detached. Specifically, a cutting machine is
arranged around the centerline S of the through-hole 14, to cut the
base material 12 at the opening of the through-hole 14 together
with the weld part 15. Thereafter, a cut groove surface is
externally observed by a camera, and size measurement and PT
testing (penetrant testing) are performed. Accordingly, the removed
concave portion 17 is formed based on the symmetrical shape around
the centerline S in a hemispherical concave portion in the lower
head 11 of the reactor vessel 10. Because the removed concave
portion 17 is formed around the centerline S, high accuracy can be
ensured.
[0080] The overlay weld part 18a of the weld part 18 is provided
next. Specifically, a backing plug is fitted to a portion where the
through-hole 14 is opened in the removed concave portion 17, to
prevent an overlay weld from entering into the through-hole 14.
Thereafter, a heater is fitted along the inner surface of the lower
head 11, which is an outer edge of the removed concave portion 17,
to perform preheating before buttered welding (for example, to
150.degree. C. or higher). A welding apparatus is arranged around
the centerline S to perform buttered welding. Thereafter, the
heater is fitted along the inner surface of the lower head 11,
which is the outer edge of the removed concave portion 17, and
along the surface of the overlay weld part 18a, to perform heat
treatment (for example, to 230.degree. C. to 290.degree. C.).
Centering and positioning of a plug cutting and removing device are
then performed with respect to the center of the through-hole 14,
the backing plug is cut and removed, and machining of the
through-hole 14 is performed. The heater is then fitted along the
inner surface of the lower head 11, which is the outer edge of the
removed concave portion 17, and along the surface of the overlay
weld part 18a, and a heater is arranged inside the through-hole 14
to perform heat treatment after buttered welding (for example, to
595.degree. C. to 710.degree. C.). It can be considered that the
heat treatment after welding is not required by performing the
buttered welding according to the temper bead welding method.
Thereafter, the cutting device is arranged around the centerline S
to form a groove. A groove surface is externally observed by the
camera, and size measurement and PT testing (penetrant testing) are
performed. Accordingly, the overlay weld part 18a is formed based
on the symmetrical shape around the centerline S inside the removed
concave portion 17. Because the overlay weld part 18a is formed
around the centerline S, high accuracy can be ensured.
[0081] Anew nozzle 20 is inserted into the through-hole 14 from the
inside of the reactor vessel 10.
[0082] The joint weld part 18b of the weld part 18 is then formed.
Specifically, the welding apparatus is arranged around the
centerline S to perform joint welding. It is then confirmed if
there is any collapse of the nozzle 20 by the camera. Thereafter, a
finishing device is arranged around the centerline S to perform
finishing work. The PT testing (penetrant testing) of the joint
welding is performed. Accordingly, the joint weld part 18b is
formed in the symmetrical shape around the centerline S between the
nozzle 20 and the overlay weld part 18a. Because the joint weld
part 18b is formed around the centerline S, high accuracy can be
ensured. As a result, the new nozzle 20 is mounted on the reactor
vessel 10.
[0083] In this manner, the nozzle mounting structure according to
the third embodiment described above includes the removed concave
portion 17 in which the base material 12 on the inner surface side
of the reactor vessel 10 is removed based on the symmetrical shape
around the centerline S of the nozzle 20, the overlay weld part 18a
welded to the inner surface of the removed concave portion 17
around the centerline S, and the joint weld part 18b for welding
the nozzle 20 inserted into the removed concave portion 17 to the
overlay weld part 18a around the centerline S.
[0084] According to the nozzle mounting structure, grooving of the
removed concave portion 17, positioning of the nozzle 20, and
welding of the nozzle 20 with respect to the reactor vessel 10 can
be performed around the centerline S of the nozzle 20, thereby
enabling to facilitate mounting of the nozzle 20.
[0085] Further, as shown in FIG. 7, in the nozzle mounting
structure according to the third embodiment, it is desired that the
nozzle 20 is divided into the outer nozzle 20a including a welded
portion by the joint weld part 18b and extending to the outside of
the reactor vessel 10, and the inner nozzle 20b arranged inside of
the reactor vessel 10, which does not include the welded portion by
the joint weld part 18b, and the outer nozzle 20a and the inner
nozzle 20b are connected to each other. Connection between the
outer nozzle 20a and the inner nozzle 20b is preferably performed
by using the screw joint 26. Alternatively, connection between the
outer nozzle 20a and the inner nozzle 20b can be performed in a
form of generally connecting tubes such as welding or caulking.
[0086] When the joint weld part 18b of the weld part 18 is
provided, if the inner nozzle 20b is divided from the outer nozzle
20a, the inner nozzle 20b is not present on the centerline S,
thereby facilitating a joint welding operation. Further, a forest
of nozzles is present on the inner side of the reactor vessel 10,
and there is only a little space between adjacent nozzles 20. A
wide work space can be ensured by dividing the inner nozzle 20b
from the outer nozzle 20a, thereby facilitating operations.
Accordingly, mounting of the nozzle 20 can be performed more
easily. To facilitate the joint welding operation, it is desired
that a divided position between the outer nozzle 20a and the inner
nozzle 20b approaches the joint weld part 18b without limit.
[0087] When the outer nozzle 20a and the inner nozzle 20b are not
divided and the nozzle 20 is integrally constructed, though not
shown, there is an advantage that a connection work between the
outer nozzle 20a and the inner nozzle 20b is not required.
[0088] In the third embodiment described above, the weld part 18
includes the overlay weld part 18a welded to the inner surface of
the removed concave portion 17 around the centerline S and the
joint weld part 18b for welding the nozzle 20 to the overlay weld
part 18a around the centerline S. However, the present invention is
not limited thereto. For example, the weld part 18 can be provided
around the centerline S for welding a new nozzle 20 inserted into
the removed concave portion 17 to the reactor vessel 10.
Specifically, in the weld part 18, the joint weld part 18b is joint
welded in a form of fixing the nozzle 20 to the reactor vessel 10,
and the overlay weld part 18a is overlay welded in such a form that
there is no weld part 18b in the removed concave portion 17 and the
surface of the base material 12 appearing on the inside of the
reactor vessel 10 is covered. Even by this configuration, the
effects of the third embodiment can be obtained.
Fourth Embodiment
[0089] A fourth embodiment of the present invention is explained
with reference to the drawings. As shown in FIG. 8, in the nozzle
mounting structure according to the present embodiment, the nozzle
20 is detached from the reactor vessel 10 shown in FIG. 1, and a
new nozzle 20 is mounted on the reactor vessel 10.
[0090] The nozzle mounting structure includes the removed concave
portion 17 in which the base material 12 at an opening of the
through-hole 14 is removed together with the weld part 15, on an
inner surface side of the reactor vessel 10 after the nozzle 20 has
been detached. The removed concave portion 17 is formed based on a
symmetrical shape around the centerline S of the nozzle 20 (the
through-hole 14 at the time of construction). The symmetrical shape
around the centerline S includes one having a circular outer
diameter around the centerline S and one having a regular polygonal
outer diameter around the centerline S.
[0091] The nozzle mounting structure also includes the flange 25 in
the new nozzle 20. The flange 25 is inserted into the removed
concave portion 17, and formed in the same symmetrical shape as
that of the removed concave portion 17 around the centerline S,
which becomes flush with the clad 13 provided on the inner surface
of the reactor vessel 10.
[0092] The nozzle mounting structure also includes a sealing part
19 for sealing between the clad 13 and the flange 25. The sealing
part 19 is constituted as a seal weld part, which is seal welded
between the clad 13 and the flange 25 around the centerline S.
Alternatively, the sealing part 19 can be a filling material to be
filled in a gap between the clad 13 and the flange 25. The filling
material includes, for example, a resin material.
[0093] The nozzle mounting structure also includes a fixing part 27
for fixing an outer surface of the nozzle 20 to the inner surface
of the through-hole 14. The fixing part 27 according to the present
embodiment has a threaded structure in which the outer surface of
the nozzle 20 and the inner surface of the through-hole 14 are
screwed together and fixed.
[0094] In a method of forming the nozzle mounting structure, first,
the inside of the reactor vessel 10 remains in an underwater
environment.
[0095] The removed concave portion 17 is formed after the existing
nozzle 20 is detached. Specifically, a cutting machine is arranged
around the centerline S of the through-hole 14, to cut the base
material 12 at the opening of the through-hole 14 together with the
weld part 15. Thereafter, the fixing part 27 is formed.
Specifically, an internal thread is machined in the through-hole
14. A cut groove surface is externally observed by a camera, and
size measurement and PT testing (penetrant testing) are performed.
Accordingly, the removed concave portion 17 and the fixing part 27
are formed based on the symmetrical shape around the centerline S
in a hemispherical concave portion in the lower head 11 of the
reactor vessel 10. Because the removed concave portion 17 and the
internal thread of the fixing part 27 are formed around the
centerline S, high accuracy can be ensured.
[0096] A new nozzle 20 is inserted into the through-hole 14 from
the inside of the reactor vessel 10, the flange 25 is fitted into
the removed concave portion 17, and the nozzle 20 is fixed in the
through-hole 14 by the fixing part (internal thread and external
thread) 27. Thereafter, it is confirmed if there is any collapse of
the nozzle 20 by the camera. The nozzle 20 is separately formed in
a factory or the like, and thus high accuracy can be ensured while
including the flange 25 and the fixing part (external thread)
27.
[0097] The sealing part (seal weld part) 19 is then provided.
Specifically, a welding device is arranged around the centerline S
to perform seal welding. Thereafter, the seal welding is inspected.
Accordingly, the gap between the flange 25 and the clad 13 is
sealed. Because the seal welding is performed around the centerline
S, high accuracy can be ensured. As a result, the new nozzle 20 is
mounted on the reactor vessel 10.
[0098] In this manner, the nozzle mounting structure according to
the fourth embodiment described above includes the removed concave
portion 17 in which the base material 12 on the inner surface side
of the reactor vessel 10 is removed based on the symmetrical shape
around the centerline S of the nozzle 20, the flange 25 provided on
the nozzle 20, formed in the symmetrical shape around the
centerline S, and inserted into the removed concave portion 17, the
sealing part 19 that seals between the clad 13 provided on the
inner surface of the reactor vessel 10 and the flange 25 around the
centerline S, and the fixing part 27 that fixes the nozzle 20 in
the through-hole 14 of the reactor vessel 10.
[0099] According to the nozzle mounting structure, grooving of the
removed concave portion 17, positioning of the nozzle 20 in the
flange 25, and, seal-up and fixation of the flange 25 with respect
to the reactor vessel 10 can be performed around the centerline S
of the nozzle 20. Accordingly, mounting of the nozzle 20 can be
easily performed. Further, because buttered welding is not
performed due to having the sealing part 19 and the fixing part 27,
any buttered welding operation and heating operation are not
required, thereby enabling to reduce operation processes
considerably and further facilitate mounting of the nozzle 20.
[0100] Particularly, according to the nozzle mounting structure of
the fourth embodiment, joint welding, buttered welding, and heat
treatment required in the first to third embodiments are not
required, construction can be performed in an underwater
environment, and an operation for creating an atmospheric
environment is not required. Therefore, operation processes can be
considerably reduced, and thus mounting of the nozzle 20 can be
performed more easily.
[0101] As another example of the fourth embodiment, it is desired
that the flange 25 is formed as shown in FIG. 9. Specifically, the
flange 25 is formed based on the same symmetrical shape as that of
the removed concave portion 17 around the centerline S, as in the
fourth embodiment. However, it is different from the fourth
embodiment that the flange 25 is formed in a symmetrical shape
around the centerline S. When the flange 25 is inserted into the
removed concave portion 17, and the nozzle 20 is fixed by the
fixing part 27, a part of the flange 25 protrudes from the clad 13
provided on the inner surface of the reactor vessel 10. The sealing
part 19 is provided in a boundary between the clad 13 and the
flange 25.
[0102] In this manner, by forming the flange 25 in the symmetrical
shape around the centerline S, when the nozzle 20 is fixed in the
through-hole 14 by the fixing part 27 having the threaded
structure, the sealing part 19 can seal between the clad 13 and the
flange 25, regardless of a threaded position. As a result, the
workability is improved, thereby enabling to facilitate mounting of
the nozzle 20 further.
[0103] As another example of the fourth embodiment, as shown in
FIGS. 10 and 11, it is desired that the nozzle 20 is divided into
the outer nozzle 20a including the flange 25 and extending to the
outside of the reactor vessel 10, and the inner nozzle 20b arranged
inside of the reactor vessel 10, which does not include the flange
25, and the outer nozzle 20a and the inner nozzle 20b are connected
to each other. Connection between the outer nozzle 20a and the
inner nozzle 20b is preferably performed by using the screw joint
26 shown in FIGS. 10 and 11. Alternatively, connection between the
outer nozzle 20a and the inner nozzle 20b can be performed in a
form of generally connecting tubes such as welding or caulking.
[0104] When the sealing part 19 is provided, if the inner nozzle
20b is divided from the outer nozzle 20a, the inner nozzle 20b is
not present on the centerline S, thereby facilitating construction
of the sealing part 19. Further, a forest of nozzles is present on
the inner side of the reactor vessel 10, and there is only a little
space between adjacent nozzles 20. A wide work space can be ensured
by dividing the inner nozzle 20b from the outer nozzle 20a, thereby
facilitating operations. Accordingly, mounting of the nozzle 20 can
be performed more easily. To facilitate construction of the sealing
part 19, it is desired that a divided position between the outer
nozzle 20a and the inner nozzle 20b approaches the flange 25
without limit.
[0105] When the outer nozzle 20a and the inner nozzle 20b are not
divided and the nozzle 20 is integrally constructed as shown in
FIGS. 8 and 9, there is an advantage that a connection work between
the outer nozzle 20a and the inner nozzle 20b is not required.
Fifth Embodiment
[0106] A fifth embodiment of the present invention is explained
with reference to the drawings. As shown in FIG. 12, in the nozzle
mounting structure according to the present embodiment, the nozzle
20 is detached from the reactor vessel 10 shown in FIG. 1, and a
new nozzle 20 is mounted on the reactor vessel 10.
[0107] The nozzle mounting structure includes the removed concave
portion 17 in which the base material 12 at an opening of the
through-hole 14 is removed together with the weld part 15, on an
inner surface side of the reactor vessel 10 after the nozzle 20 has
been detached. The removed concave portion 17 is formed based on a
symmetrical shape around the centerline S of the nozzle 20 (the
through-hole 14 at the time of construction). The symmetrical shape
around the centerline S includes one having a circular outer
diameter around the centerline S and one having a regular polygonal
outer diameter around the centerline S.
[0108] The nozzle mounting structure also includes the flange 25 in
the new nozzle 20. The flange 25 is inserted into the removed
concave portion 17, and is formed in the same symmetrical shape as
that of the removed concave portion 17 around the centerline S,
which becomes flush with the clad 13 provided on the inner surface
of the reactor vessel 10.
[0109] The nozzle mounting structure also includes the sealing part
19 for sealing between the clad 13 and the flange 25. The sealing
part 19 is constituted as a seal weld part, which is seal welded
between the clad 13 and the flange 25 around the centerline S.
Alternatively, the sealing part 19 can be a filling material to be
filled in a gap between the clad 13 and the flange 25. The filling
material includes, for example, a resin material.
[0110] The nozzle mounting structure also includes the fixing part
27 for fixing an outer surface of the nozzle 20 to an inner surface
of the through-hole 14. The fixing part 27 according to the present
embodiment has a structure in which the nozzle 20 is expanded and
an outer surface of the expanded nozzle 20 and the inner surface of
the through-hole 14 are fixed by close attachment.
[0111] In a method of forming the nozzle mounting structure, first,
the inside of the reactor vessel 10 remains in an underwater
environment.
[0112] The removed concave portion 17 is formed after the existing
nozzle 20 is detached. Specifically, a cutting machine is arranged
around the centerline S of the through-hole 14, to cut the base
material 12 at the opening of the through-hole 14 together with the
weld part 15. Thereafter, a cut groove surface is externally
observed by a camera, and size measurement and PT testing
(penetrant testing) are performed. Accordingly, the removed concave
portion 17 is formed based on the symmetrical shape around the
centerline S in a hemispherical concave portion in the lower head
11 of the reactor vessel 10. Because the removed concave portion 17
is formed around the centerline S, high accuracy can be
ensured.
[0113] A new nozzle 20 is inserted into the through-hole 14 from
the inside of the reactor vessel 10, the flange 25 is fitted into
the removed concave portion 17, and the nozzle 20 is fixed in the
through-hole 14 by the fixing part (expanded nozzle) 27.
Thereafter, it is confirmed if there is any collapse of the nozzle
20 by the camera. The nozzle 20 is separately formed in a factory
or the like, and thus high accuracy can be ensured while including
a portion for providing the flange 25 and the fixing part (expanded
nozzle) 27.
[0114] The sealing part (seal weld part) 19 is then provided.
Specifically, a welding device is arranged around the centerline S
to perform seal welding. Thereafter, the seal welding is inspected.
Accordingly, the gap between the flange 25 and the clad 13 is
sealed. Because the seal welding is performed around the centerline
S, high accuracy can be ensured. As a result, the new nozzle 20 is
mounted on the reactor vessel 10. Either of fixation and seal
welding of the nozzle 20 can be performed first.
[0115] Thus, the nozzle mounting structure according to the fifth
embodiment includes the removed concave portion 17 in which the
base material 12 on the inner surface side of the reactor vessel 10
is removed based on the symmetrical shape around the centerline S
of the nozzle 20, the flange 25 provided on the nozzle 20, formed
in the symmetrical shape around the centerline S, and inserted into
the removed concave portion 17, the sealing part 19 that seals
between the clad 13 provided on the inner surface of the reactor
vessel 10 and the flange 25 around the centerline S, and the fixing
part 27 that fixes the nozzle 20 in the through-hole 14 of the
reactor vessel 10.
[0116] According to the nozzle mounting structure, grooving of the
removed concave portion 17, positioning of the nozzle 20 in the
flange 25, and seal-up and fixation of the flange 25 with respect
to the reactor vessel 10 can be performed around the centerline S
of the nozzle 20. Accordingly, mounting of the nozzle 20 can be
easily performed. Further, because buttered welding is not
performed due to having the sealing part 19 and the fixing part 27,
any buttered welding operation and heating operation are not
required, thereby enabling to reduce operation processes and
facilitate mounting of the nozzle 20.
[0117] Particularly, according to the nozzle mounting structure of
the fifth embodiment, joint welding, buttered welding, and heat
treatment required in the first to third embodiments are not
required, construction thereof can be performed in an underwater
environment, and an operation for creating an atmospheric
environment is not required. Therefore, operation processes can be
considerably reduced, and thus mounting of the nozzle 20 can be
performed more easily.
[0118] As another example of the fifth embodiment, as shown in FIG.
13, it is desired that the nozzle 20 is divided into the outer
nozzle 20a including the flange 25 and extending to the outside of
the reactor vessel 10, and the inner nozzle 20b arranged inside of
the reactor vessel 10, which does not include the flange 25, and
the outer nozzle 20a and the inner nozzle 20b are connected to each
other. Connection between the outer nozzle 20a and the inner nozzle
20b is preferably performed by using the screw joint 26 shown in
FIG. 13. Alternatively, connection between the outer nozzle 20a and
the inner nozzle 20b can be performed in a form of generally
connecting tubes such as welding or caulking.
[0119] When the sealing part 19 is provided, if the inner nozzle
20b is divided from the outer nozzle 20a, the inner nozzle 20b is
not present on the centerline S, thereby facilitating construction
of the sealing part 19. Further, a forest of nozzles is present on
the inner side of the reactor vessel 10, and there is only a little
space between adjacent nozzles 20. A wide work space can be ensured
by dividing the inner nozzle 20b from the outer nozzle 20a, thereby
facilitating operations. Accordingly, mounting of the nozzle 20 can
be performed more easily. To facilitate construction of the sealing
part 19, it is desired that a divided position between the outer
nozzle 20a and the inner nozzle 20b approaches the flange 25
without limit.
[0120] When the outer nozzle 20a and the inner nozzle 20b are not
divided and the nozzle 20 is integrally constructed as shown in
FIG. 12, there is an advantage that any connection work between the
outer nozzle 20a and the inner nozzle 20b is not required.
Sixth Embodiment
[0121] In a nozzle mounting structure according to a sixth
embodiment of the present invention, the nozzle 20 is detached from
the reactor vessel 10 shown in FIG. 1, and a new nozzle is mounted
on the reactor vessel 10.
[0122] The nozzle mounting structure includes a removed concave
portion in which a base material at an opening of a through-hole is
removed together with a weld part, on an inner surface side of a
reactor vessel after a nozzle has been detached, though not shown.
The removed concave portion is formed based on a symmetrical shape
around a centerline of the nozzle (the through-hole at the time of
construction). The symmetrical shape around the centerline includes
one having a circular outer diameter around the centerline S and
one having a regular polygonal outer diameter around the centerline
S.
[0123] The nozzle mounting structure also includes a flange in the
new nozzle. The flange is inserted into the removed concave
portion, and is formed in the same symmetrical shape as that of the
removed concave portion around the centerline, which becomes flush
with a clad provided on the inner surface of the reactor
vessel.
[0124] The nozzle mounting structure also includes a weld part for
welding the nozzle to the reactor vessel. The weld part includes an
overlay weld part welded to an outer surface of the existing weld
part 16 (see FIG. 1) on an outer surface side of the reactor
vessel, based on a normal line on a hemispherical convex outer
surface in a lower head of the reactor vessel, and a joint weld
part in which the nozzle protruding from the weld part 16 and the
overlay weld part are welded together based on the normal line. In
the overlay weld part, stainless steel or Ni-base alloy is overlay
welded to the outer surface of the weld part 16, and in the joint
weld part, stainless steel or Ni-base alloy is joint welded to a
slotted portion of the overlay weld part.
[0125] According to the nozzle mounting structure of the sixth
embodiment, machining of the removed concave portion and
positioning of the nozzle in the flange can be performed around a
centerline of the nozzle, and welding of the nozzle to the reactor
vessel can be performed based on the normal line on the outer
surface of the lower head, thereby enabling to facilitate mounting
of the nozzle. Particularly, according to the nozzle mounting
structure of the sixth embodiment, any welding operation on the
inside of the reactor vessel is not required, and the welding
operation is performed only on outside of the reactor vessel.
Accordingly, mounting of the nozzle can be performed more
easily.
Seventh Embodiment
[0126] In a nozzle mounting structure according to a seventh
embodiment of the present invention, the nozzle 20 is detached from
the reactor vessel 10 shown in FIG. 1, and a new nozzle is mounted
on the reactor vessel 10.
[0127] The nozzle mounting structure includes a large-diameter
through-hole in which a through-hole is expanded and a base
material is removed together with a weld part, on an inner surface
side of a reactor vessel after a nozzle has been detached, although
not shown in the drawings. The large-diameter through-hole is
formed based on a symmetrical shape around a centerline of the
nozzle (the through-hole at the time of construction). The
symmetrical shape around the centerline includes one having a
circular outer diameter around the centerline S and one having a
regular polygonal outer diameter around the centerline S.
[0128] The nozzle mounting structure also includes a sleeve. The
sleeve is a cylindrical body formed in the same symmetrical shape
as an inner surface of the large-diameter through-hole around the
centerline. The sleeve is inserted into the large-diameter
through-hole, follows an inner circumference of the large-diameter
through-hole, and becomes flush with a clad provided on the inner
surface of the reactor vessel and an outer surface of the reactor
vessel.
[0129] The nozzle mounting structure includes a flange in the new
nozzle. The flange is fitted into the inside of the sleeve inserted
into the large-diameter through-hole, and protrudes toward the
inner surface and outer surface sides of the reactor vessel. The
flange is formed based on the same symmetrical shape as the inner
surface of the sleeve around the centerline.
[0130] The nozzle mounting structure also includes a weld part for
welding the nozzle to the reactor vessel. The weld part includes an
overlay weld part welded to an outer surface side of the reactor
vessel, in which the weld part 16 (see FIG. 1) is removed, based on
a normal line on a hemispherical convex outer surface in a lower
head of the reactor vessel, and a joint weld part in which the
nozzle protruding from the large-diameter through-hole and the
overlay weld part are welded together based on the normal line. In
the overlay weld part, stainless steel or Ni-base alloy is overlay
welded to the outer surface of the reactor vessel, and in the joint
weld part, stainless steel or Ni-base alloy is joint welded to a
slotted portion of the overlay weld part.
[0131] According to the nozzle mounting structure of the seventh
embodiment, machining of the large-diameter through-hole and
positioning of the nozzle in the flange can be performed around the
centerline of the nozzle, and welding of the nozzle to the reactor
vessel can be performed based on the normal line on the outer
surface of the lower head, thereby enabling to facilitate mounting
of the nozzle. Particularly, according to the nozzle mounting
structure of the seventh embodiment, any welding operation on the
inside of the reactor vessel is not required, and the welding
operation is performed only on the outside of the reactor vessel.
Accordingly, mounting of the nozzle can be performed more
easily.
INDUSTRIAL APPLICABILITY
[0132] As described above, the nozzle mounting structure according
to the present invention is suitable for easily performing mounting
of a nozzle.
REFERENCE SIGNS LIST
[0133] 10 reactor vessel [0134] 11 lower head [0135] 12 base
material [0136] 13 clad [0137] 14 through-hole [0138] 17 removed
concave portion [0139] 18 weld part [0140] 18a overlay weld part
[0141] 18b joint weld part [0142] 19 sealing part [0143] 20 nozzle
[0144] 20a outer nozzle [0145] 20b inner nozzle [0146] 25 flange
[0147] 26 screw joint [0148] 27 fixing part [0149] N normal line
[0150] S centerline
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